This invention relates to an actuator, in particular an actuator to which a pressure is input and a displacement according to the input pressure is extracted.
A piezo actuator or bellows actuator has been proposed as a nanoactuator in which ultrahigh precision positioning is possible so that a minute, high precision displacement can be extracted.
A piezo actuator is a piezoelectric element which is polarized in a predetermined direction, and extracts a displacement using a distortion deformation by applying a voltage to this piezoelectric element. On the other hand, a bellows actuator is an actuator wherein positional control is performed by feedback of a force applied to a bellows and a distortion amount of the bellows due to this force.
In a prior art piezoactuator, since there is a large amount of hysteresis, closed loop control must be performed. Also, since the piezoactuator has a high development cost, it is limited to applications which assume mass production or applications where high cost can be tolerated, and it cannot be used for applications which do not assume mass production or low-cost applications. Moreover, with a piezoactuator, if the applied voltage is not increased, a large displacement amount cannot be extracted.
On the other hand, in the case of a bellows actuator, since the distortion amount determines the displacement amount, temperature drift increases. Also, it is easily affected by external noise, closed loop control is indispensable for increasing precision, and it is difficult to manufacture it at low cost.